Sales in many neighborhoods shot up considerably in the second quarter of 2010 — by as much as 40 percent, according to a new market survey released today.

“The housing market has essentially stabilized — at least, as opposed to the dark days” of 2007 and 2008, said Jonathan Miller, president of the appraisal firm Miller Samuel, which releases the sales analysis every quarter.

Of course, there’s a but.

The uptick in sales is partly due to this year’s tax credits, Miller added, referring to the incentives of up to $8,000 that first-time buyers got if they closed a deal by June 30 this year.

Those breaks may be why the report shows an almost 40-percent increase in the number of home sales in Williamsburg and Greenpoint this quarter, from 127 to 177.

The average sale price in those neighborhoods took another sidestep, just like last quarter — another sign that there’s a new trend on the market: though sales activity is up, the market is taking a sidestep because there’s such a high concentration of homes for sale (especially in areas like Williamsburg and Greenpoint).

Here’s a roundup of the report’s main findings:

• The price of the average one- to three-family household in so-called “Brownstone Brooklyn” — a swath from Brooklyn Heights to Windsor Terrace — decreased by one percent in the second quarter, from $1.4 million to $1.3 million, an “insignificant” amount according to Miller, given that the steep declines of the recent past have largely been checked. Indeed, the “trend” shows that the worst may indeed be over.

• Williamsburg and Greenpoint not only saw the big increase in sales, but also a nearly five-percent increase in the average sale price of a home, from $600,000 to $628,000.

Previously, Williamsburg and Greenpoint’s numbers had been tracking downward because so many of the neighborhoods’ luxury units were either not selling, or selling for bust-deflated prices. Now, because of the incentives, they’re starting to sell for more — yet another sign that the market is stabilizing. Miller said that the next two quarters will be interesting, once the tax incentives are out of the way and the real housing market kicks back in.

“Will the Brooklyn market be able to stand on its own two feet at that point?” he said. “I’m skeptical.”

• If you’re going to buy, go to the new Williamsburg: Bushwick and Bedford-Stuyvesant, where the average sale price dropped by another three percent (for the third quarter in a row, by the way) and the average one- to three-family home goes for $367,275.